The overall aim of our research program is to achieve an increased understanding of the range of structural diversity in the immune system. In line with this general goal, we are carrying out the following projects. 1. The structure and function of immunoglobulin variants. We have demonstrated that the crystallizable human IgGl myeloma protein Dob has a deletion of 15 amino acids in the hinge region of its heavy chain. We have also determined the complete amino acid sequence of the variable region of the heavy chain, and are presently carrying out studies on the sequence of the light chain. We plan to investigate whether the hinge deletion affects the ability of the protein to activate the complement system. 2. Studies on the variable regions of murine lambda 2 chains. We are examining the pattern of diversity in amino acid sequence of variable regions of the lambda 2 class. The long-term goal is to determine whether somatic processes may play a role in the generation of antibody diversity. 3. The immune system in a developing amphibian. We wish to determine the major structural features of the various immunoglobulins in the bullfrog, Rana catesbiana, in order to obtain insight into the evolution of the immune response.